Parts

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Line Power With No Transformer

February 24, 2025 by 43 Comments

Normally, when you want a low DC voltage from the AC line, you think about using a transformer of some kind. [RCD66] noticed that an AC monitor meter must have some sort of power supply but had no transformers in sight. That led to an exploration of how those work and how you can use them, too. You can watch the work in the video below.

Sensibly, there is a transformer in the test setup — an isolation transformer to make it safe to probe the circuit. But there’s no transformer providing voltage changes. Isolation is important even if you are taking apart something commercial that might be trasformerless.

The circuit is simple enough: it uses a capacitor, a resistor, and a pair of diodes (one of them a zener diode). He uses this basic circuit to drive simple regulators with input and output filter capacitors. We’ve seen many variations on this design over the years.

You can’t draw a lot of power through this arrangement. But sometimes it is all you need. However, this is pretty dangerous, as we’ve discussed before. Be sure you understand exactly what the risks are before you decide to build something like this.

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Lathe And Laser Team Up To Make Cutting Gear Teeth Easier

February 14, 2025 by 25 Comments

Fair warning: watching this hybrid manufacturing method for gear teeth may result in an uncontrollable urge to buy a fiber laser cutter. Hackaday isn’t responsible for any financial difficulties that may result.

With that out of the way, this is an interesting look into how traditional machining and desktop manufacturing methods can combine to make parts easier than either method alone. The part that [Paul] is trying to make is called a Hirth coupling, a term that you might not be familiar with (we weren’t) but you’ve likely seen and used. They’re essentially flat surfaces with gear teeth cut into them allowing the two halves of the coupling to nest together and lock firmly in a variety of relative radial positions. They’re commonly used on camera gear like tripods for adjustable control handles and tilt heads, in which case they’re called rosettes.

To make his rosettes, [Paul] started with a block of aluminum on the lathe, where the basic cylindrical shape of the coupling was created. At this point, forming the teeth in the face of each coupling half with traditional machining methods would have been tricky, either using a dividing head on a milling machine or letting a CNC mill have at it. Instead, he fixtured each half of the coupling to the bed of his 100 W fiber laser cutter to cut the teeth. The resulting teeth would probably not be suitable for power transmission; the surface finish was a bit rough, and the tooth gullet was a little too rounded. But for a rosette, this was perfectly acceptable, and probably a lot faster to produce than the alternative.

In case you’re curious as to what [Paul] needs these joints for, it’s a tablet stand for his exercise machine. Sound familiar? That’s because we recently covered his attempts to beef up 3D prints with a metal endoskeleton for the same project.

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A Tiny Tapeout SDR

February 11, 2025 by 4 Comments

The Tiny Tapeout custom ASIC project has been around for a while now, and has passed through several iterations of its production. On each Tiny Tapeout chip are multiple designs, each representing an individual project, and in use the chip is configured to present that project to its pins. Given enough Tiny Tapeout chips it was inevitable that someone whould eventually make a project using two such functions, and here’s [Sylvain Munaut] with an SDR using Tiny Tapeouts 6 and 7.

At its heart is [Carsten Wulff]’s 8 bit ADC from Tiny Tapeout 6, fed by [Kolos Koblász]’s Gilbert cell RF mixer from Tiny Tapeout 7. There’s a local oscillator provided by an RP2040, and a USB interface board which sends the data to a host computer where GNU Radio does the maths. On the bench it’s receiving an FM signal generated around 30MHz by a signal generator, followed by some slightly indistinct commercial radio stations.

It’s clear that there are many better SDRs than this one, and that (as yet) Tiny Tapeout is perhaps not the radio enthusiast’s choice. But it does demonstrate beautifully how the chips are more than just curios, and we’re definitely in the era of useful on-demand ASICs.

The video is below the break, meanwhile you can learn about Tiny Tapeout from [Matt Venn]’s Supercon talk.

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Precision Reference Puts Interesting Part To Work

February 11, 2025 by 8 Comments

Interesting parts make for interesting projects, and this nifty precision voltage reference has some pretty cool parts, not to mention an interesting test jig.

The heart of [Gaurav Singh]’s voltage reference is an ADR1399, precision shunt reference from Analog Devices. The datasheet makes for pretty good reading and reveals that there’s a lot going on inside the TO-49 case, which looks unusually large thanks to a thick plastic coat. The insulation is needed for thermal stability for the heated Zener diode reference. The device also has a couple of op-amps built in, one that provides closed-loop voltage control and another that keeps the internal temperature at a toasty 95°C. The result is a reference that’s stable over a wide range of operating conditions.

[Gaurav]’s implementation maximizes this special part’s capabilities while making it convenient to use. The PCB has a precision linear regulator that accepts an input voltage from 16 V to 20 V, plus a boost converter that lets you power it from USB-C. The board itself is carefully designed to minimize thermal and mechanical stress, with the ADR1399 separated from the bulk of the board with wide slots. The first video below covers the design and construction of an earlier rev of the board.

One problem that [Gaurav] ran into with these boards was the need to age the reference with an extended period of operation. To aid in that, he built a modular test jig that completed PCBs can be snapped into for a few weeks of breaking in. The jigs attach to a PCB with pogo pins, which mate to test points and provide feedback on the aging process. See the second video for more details on that.

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Breaking: USPS Halts Inbound Packages From China And Hong Kong Posts

February 5, 2025 by 104 Comments

Update: The USPS has now resumed acceptance of inbound packages from China. According to the updated Service Alert, they are currently working with Customs and Border Protection to “implement an efficient collection mechanism for the new China tariffs.’

Some troubling news hit overnight as the United States Post Office announced via a terse “Service Alert” that they would suspend acceptance of inbound parcels from China and Hong Kong Posts, effective immediately.

The Alert calls it a temporary suspension, but gives no timeline on when service will be restored. While details are still coming together, it seems likely that this suspension is part of the Trump administration’s Chinese tariff package, which went into effect at midnight.

Specifically, the administration looks to close the “de minimis” exemption — a loophole which allowed packages valued under $800 USD to pass through customs without having to pay any duties or fees. Those packages will now not only be subject to the overall 10% tax imposed by the new tariff package, but will now have to be formally processed through customs, potentially tacking on even more taxes and fees.

The end result is that not only will your next order of parts from AliExpress be more expensive, but it’s likely to take even longer to arrive at your door. Of course, this should come as no surprise. At the end of the day, this is precisely what the administration aims to accomplish with the new tariffs — if purchasing goods from overseas is suddenly a less attractive option than it was previously, it will be a boon to domestic suppliers. That said, some components will be imported from China regardless of who you order them from, so those prices are still going to increase.

Other carriers such as FedEx and UPS will also have to follow these new rules, but at the time of this writing, neither service had released a statement about how they intend to comply.

How 3D Printing Helps Bring USS Cod Memorial To Life

February 5, 2025 by 3 Comments

The USS Cod is a Gato-class submarine that saw combat in the Second World War and today operates as a museum ship in Cleveland, Ohio. While many other surviving WWII-era subs were cut into pieces or otherwise modified for public display, Cod is notable for being intact and still in her wartime configuration. It’s considered to be one of the finest submarine restorations in the world, and in a recent video from their official YouTube page, we get a look at how 3D printing is used to keep the 82 year old submarine looking battle-ready.

In the video below, President of the USS Cod Submarine Memorial [Paul Farace] is joined by one of the volunteers who’s been designing and printing parts aboard the submarine. While the Cod is in remarkable condition overall, there’s no shortage of odd bits and pieces that have gone missing over the sub’s decades of service.

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Homebrew Foil And Oil Caps Change Your Guitar’s Tone

February 4, 2025 by 47 Comments

How any string instrument sounds depends on hundreds of factors; even the tiniest details matter. Seemingly inconsequential things like whether the tree that the wood came from grew on the north slope or south slope of a particular valley make a difference, at least to the trained ear. Add electronics into the mix, as with electric guitars, and that’s a whole other level of choices that directly influence the sound.

To experiment with that, [Mark Gutierrez] tried rolling some home-brew capacitors for his electric guitar. The cap in question is part of the guitar’s tone circuit, which along with a potentiometer forms a variable low-pass filter. A rich folklore has developed over the years around these circuits and the best way to implement them, and there are any number of commercially available capacitors with the appropriate mojo you can use, for a price.

[Mark]’s take on the tone cap is made with two narrow strips of regular aluminum foil separated by two wider strips of tissue paper, the kind that finds its way into shirt boxes at Christmas. Each of the foil strips gets wrapped around and crimped to a wire lead before the paper is sandwiched between. The whole thing is rolled up into a loose cylinder and soaked in mineral oil, which serves as a dielectric.

To hold the oily jelly roll together, [Mark] tried both and outer skin of heat-shrink tubing with the ends sealed by hot glue, and a 3D printed cylinder. He also experimented with a wax coating to keep the oily bits contained. The video below shows the build process as well as tests of the homebrew cap against a $28 commercial equivalent. There’s a clear difference in tone compared to switching the cap out of the circuit, as well as an audible difference in tone between the two caps. We’ll leave the discussion of which sounds better to those with more qualified ears; fools rush in, after all.

Whatever you think of the sound, it’s pretty cool that you can make working capacitors so easily. Just remember to mark the outer foil lead, lest you spoil everything.

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